The present invention relates to an electron beam excited plasma apparatus which irradiates a material with ions generated by an electron beam.
As disclosed in Japanese Patent Laid-Open Application No. 290629-1986, ion irradiation apparatus are used for performing dry etching to integrated circuits such as IC and LSI and the like. Currently known ion irradiation apparatus are systems which generate a plasma by a DC (direct current) discharge, RF (high frequency) discharge, ECR (electron cyclotron resonance) or an electron beam or the like, use the action of an electric field to draw only ions from the plasma, and which irradiate these ions to a material. When ions are irradiated to a material such as an 8-inch Si wafer which has a large diameter and dry etching is performed with respect to the Si wafer, large marks or other damage must not be caused to the Si wafer. This requires satisfying the mutually opposing conditions of uniformly irradiating an ion irradiation having a large current density across a large sectional surface and in a low energy ion region.
However, with a conventional ion irradiation apparatus, increasing the ion current density in the low energy ion region means that it is not possible to have uniformity for a large sectional area.
In order to solve the problem of these mutually opposing conditions, there has been the development of an electron beam excited plasma technology which enables the generation of a high-density plasma which produces a large ion current density. When a material is held at a floating potential, the influence of the large electron beam component causes the ion energy to become higher in the vicinity of the axis of the electron beam at the center of the material, and furthermore, it is not possible to have a uniform ion current density.